This invention relates in general to turbines and in particular to a new and useful construction and method for maintaining a uniform clearance of labyrinth seals arranged at each end of a rotatable turbine shaft.
The invention relates to a flow machine, in particular a superheated gas turbine, the machine housing of which is equipped on both sides with a labyrinth seal sealing the rotor shaft by means of a sealing fluid, and to controlling the labyrinth seal clearance automatically and continuously.
Several and different problems regarding the housing and rotor shaft mounting occur in such machines, and numerous attempts to avoid or remedy the known difficulties have not been lacking.
In single housing flow machines, and even more so in machines having two or more housings, such as turbines or compressors, the problem of providing an adjustment possibility for the housing parts to make their exact and simple alignment possible crops up even when aligning the housing parts in assembly.
Another problem encountered in such machines also is that sometimes changes in the foundations, such as settling of the floor, take place, which can effect the precise horizontal alignment of the machine or machine aggregates. In such cases a realignment must be carried out which often is associated with considerable engineering expense.
Securing exact centering and maintaining the clearances when heat expansions of the machine occur represents a very serious problem. For example, to make readjustments of housing parts possible, it is suggested in DE-AS No. 12 89 535 to support these parts relative to each other by means of adjusting screws and exchangable shims of varying thickness. Another, similar suggestion made in the German design patent No. 71 24 691 relates to the same problem and shows an arrangement of spherical adjusting parts in conjunction with height adjustable immersion nuts.
The aligning problem, in particular of machine sets with several housings, is also the basis of German patent DE-AS No. 23 25 642, the object of which is the facilitation or improvement of the relative alignment of the power turbine rotor in the power turbine housing. Proposed for this purpose is suspending the turbine from two trunnions and having the gas generator supported by a movable support structure. A similar suspension is also shown in German patent DE-OS No. 26 17 024. Therein, the turbine stator housing is suspended so as to be freely expandable from flanges of the outer engine housing by means of radially oriented bolts.
The axial alignment of a multihousing or multiunit machine set such as a turbo group consisting of a helium high temperature turbine with a compressor and a generator involves special difficulties. According to DE-OS No. 27 17 617 it is suggested that there be disposed between the foundation and the turbo-group height-adjustable and axially movable supports which should engage lateral claws of the turbo group and be height-adjustable hydraulically or mechanically. At least four such height-adjustable supports are provided for each machine housing. Such an arrangement makes it possible to align the housings of several machines belonging to a turbo group axially and also to readjust this alignment when needed.
Apart from the difficulties of aligning such flow machines in assembly as discussed in the above publications, or also the difficulties of the misalignments developing in the course of operation as well as the further problem, particularly occurring in flow machines highly stressed thermally, and also of the difficulties involved due to the possibility of tensions and impermissable changes in the required clearances resulting from thermal stress of housing and subassembly components, an additional difficulty exists that adequate vibration damping in such machines, taking into account varying operating conditions, is often unattainable when the known bearing arrangements are employed.